The first legal attempt to prevent the prime minister initiating Britain’s withdrawal from the European Union is to be heard later this month.

A high court judge, Mr Justice Cranston, has set 19 July for a preliminary hearing of the judicial review challenge brought on behalf of the British citizen Deir Dos Santos.

The claim argues that only parliament – not the prime minister – can authorise the signing of article 50 of the Lisbon treaty, which begins the UK’s formal withdrawal process.

Other legal claims making a similar point are also being prepared by the law firm Mishcon de Reya. Brexit supporters staged a demonstration outside their London office on Thursday with a banner and placards declaring “‘Invoke article 50 now” and “‘Uphold the Brexit vote”.

The politically sensitive hearing will be heard by two judges in the divisional court. The Dos Santos claim argues that: “The result of the referendum is not legally binding in the sense that it is advisory only and there is no obligation [on the government] to give effect to the referendum decision. However the prime minister has stated on numerous occasions that it is his intention to give effect to the referendum decision and organise the United Kingdom’s withdrawal from the European Union.

“The extract from the prime minister’s resignation speech ... makes it clear that [the government] is of the view that the prime minister of the day has the power under article 50 (2) of the Lisbon treaty to trigger article 50 without reference to parliament.”

That decision, it claims, is “ultra vires” – beyond the legitimate powers of the government – because under “the UK’s constitutional requirements”, notification to the European Union council of withdrawal “can only be given with the prior authorisation of the UK parliament”.

Dominic Chambers QC, an expert in international and commercial law from Maitland Chambers in London, is acting for Dos Santos.

The claim refers to recent statements from the Foreign Office explaining that it is parliament that has the power to repeal the European Communities Act 1972. It also argues that the royal prerogative – powers employed by the prime minister – cannot be used to undermine parliamentary statute.

A vote to leave is a vote to needlessly destroy our legal system | Elizabeth Prochaska

In a separate development, Anthony Eskander, a criminal barrister at Church Court Chambers in London, has posted an opinion arguing that politicians supporting the Vote Leave campaign might have opened themselves up to legal action for alleged misrepresentations over claims that quitting the EU would allow an extra £350m to be spent on the NHS.

It claims politicians might have committed offences of misconduct in public office by promoting the £350m claim. The figure has been called “potentially misleading” by the independent UK Statistics Authority, for failing to take into account the UK’s rebate from the EU. Vote Leave denied during the referendum campaign that it was misleading the public.

Harry Shindler, 94, who tried to overturn the ban preventing those who have lived overseas for more than 15 years from voting, has threatened to challenge the validity of the referendum result at the United Nations.

More than 700,000 Britons resident abroad are estimated to have been denied a chance to register for the ballot. In the run-up to the referendum, the high court, appeal court and supreme court threw out Shindler’s legal claims on the technical grounds of whether EU law permitting freedom of movement applied.

Speaking from his home in San Benedetto on Italy’s Adriatic coast, the war veteran who was awarded an MBE in 2014 for his services to Anglo-Italian relations, told the Guardian: “We feel we should have taken part in the referendum. We can’t go back to the courts. We have been to all the courts that we can in England. So now we will go to the UN human rights commission in Geneva, asking them to declare the result of the referendum null and void. I am preparing a case now that will be with the United Nations.

“It’s contrary to [article 21 of ] the UN Declaration of Human Rights [in 1948] which says that citizens have a right to take part in the election of the government of their country. Universal suffrage is supposed to mean everybody. I’m doing this in the knowledge that I am supported by expats throughout Europe, I am in touch with people in France, Spain, Portugal and Germany.”